SEO is a process to increase the ranking and traffic of your website in search engines using your targeted keywords by natural way means use unique content and build quality backlinks for your website.
SEO is many types like SMO, SEM, Organic
SEO.. etc.
PPC or SEM is the part of
SEO and it is use for popular your products, Business, brand and website by paid search engines. PPC is the surety to show your website in top results related to your targeted keywords searches.